Anthurium rionegrense Matuda,

Anales Inst. Biol. Univ. Nac. Mexico 36: 109, Fig. 4. 1966. TYPE: Mexico. Oaxaca: Río Negro between the stales of Chiapas and Oaxaca, MacDougall 459 (MEXU).

Epiphyte; stems short.

LEAVES with petioles 19-28 cm long, sulcate adaxially; the geniculum 1.5 cm long; blades subcoriaceous, ovate, 20-22 cm long, 16-23 cm wide, gradually acuminate at apex, broadly lobed at base, broadest at point of petiole attachment; the anterior lobe 14-15 cm long; posterior lobes 7-9 cm long; sinus hippo-crepiform, rounded at apex; midrib raised above and below; basal veins 4-6 pairs, fourth to sixth coalesced 1.5-2.1 cm; posterior ribs naked; primary lateral veins 2-4 per side, departing midrib at 50° angle, raised above and below; collective vein arising from first basal vein, 8-10 mm from margin.

INFLORESCENCE longer than leaves;peduncle terete, 27-61 cm long; spathe linear-lanceolate, 2.5-8.5 cm long, 5-12 mm wide, broadest below middle, acuminate at apex, clasping at base; spadix green, 2-5 cm long, 3-5 mm diam. at base, 2 mm diam. at apex; the flowers rhombic, 4 mm long, 2.8 mm wide, the sides straight; 4 flowers visible in the principal spiral, 5 flowers visible in the alternate spiral; tepals punctate, lateral tepals 1.5 mm wide, inner margin convex, turned up; pistil emergent, green; stigma slillike, 7 mm long; stamens held over pistil; anthers cream, ovoid, 3 mm long, 4 mm wide; thecae cllipsoid, scarcely divaricate.

INFRUCTESCENCE not seen. Figs. 161 and 163.

Anthurium rionegrenseK known only from the Río Negro and Río Mono Blanco in the vicinity of the Oaxaca and Chiapas frontiers. Neither location has been located so the elevation is uncertain. but most elevations along the western Chiapas border range from 200 to 1,000 m, and only Cerro Baul on the Oaxaca border, southwest ofCintalapa, is very high, extending up to about 1,800 m.
The species is a member of the section Belolonchium and is recognized by its thin, broadly ovate leaves with short, linear raphide cells visible on the upper surface on drying and by its slender tapered, greenish spadix with the tepals thin and clear along the inner margins and otherwise distinctly punctate with raphide cells.
Anthurium rionegrense is perhaps most easily confused with two other thin leaved, basically ovate-cordate species, A. ovandense and A. !ezamae. Anthurium ovandense diners in having the anterior lobe usually concave along the margins whereas A. lezamae differs in being more narrowly ovate and in having an alveolate epidermal pattern on drying.